Automatic Segmentation of the Structures in the Nasal Cavity and the Ethmoidal Sinus for the Quantification of Nasal Septal Deviations
Nasal septal deviations are a well-known and widespread problem. According to the American Academy of Otolaryngology 80% of the population have a nasal septal deviation. Its level of severity can range from the person not being aware of it to respiratory obstruction and choking. It is therefore necessary to distinguish those patients at risk. For a proper diagnosis, the amount and location of the deviation have to be considered, but also the shape and changes in the surrounding turbinates. The segmentation of the structures of interest is an important step to reduce subjectivity in the diagnosis. Unfortunately, due to their variable and tortuous shape manual segmentation is time consuming. In this paper, the first method for the automatic segmentation of the structures in the nasal cavity and ethmoidal sinus is presented. A coupled shape model of the nasal cavity and paranasal sinus regions is trained and used to detect the corresponding regions in new CT images. The nasal septum is then segmented using a novel slice-based propagation technique. This segmentation allows the additional separation and segmentation of the left and right nasal cavities and ethmoidal sinuses and their structures by means of an adaptive thresholding with varying boundary sizes. The method has been evaluated in 10 CT images obtaining promising results for the nasal septum (DICE: 87.71%) and for the remaining structures (DICE: 72.01% - 73.01%). Based on the resulting segmentations, a web-based diagnosis tool has been designed to quantify the septal deviation using three metrics proposed by clinical experts.